Power Counter +1
From Archon Arcana - The KeyForge Wiki
When a creature is given a “+1 power counter,” one such status counter is placed on the creature. For each of these counters that is on a creature, that creature’s power is increased by one.
Note: The original Call of the Archons starter set used +1 power cards, instead of cardboard counters. These cards are used exactly like +1 power counters.
—KeyForge Master Rulebook v17 April 2023
Some abilities in KeyForge grant creatures additional power; that power gain is contingent on the creature providing the ability remaining in play. For example, if Panpaca, Anga is in a player's battleline, as long as Panpaca, Anga is in play, creatures to the right of Panpaca, Anga get +2 power. If Panpaca, Anga leaves play, those creatures return to their normal printed power (providing there are no other upgrades on them). Other abilities give +1 Power Counters that will increase the creature's power as long as the power token is present on the creature. For example, the ability of Grovekeeper gives each of its neighbors a +1 Power counter at the end of Grovekeeper's controller's turn. If Grovekeeper leaves play, the power counter that was granted remains. For this reason, it is not recommended to track temporary power increases (like that of Panpaca, Anga) using power counters.